In this first exercise you will track a shot in order to stabilize it, meaning stopping it from moving. To give you something to stabilize, bring a sequence in from the disk.
1 . Using a Read node, load the sequence named stabilize.####.tif, from the chapter05 directory, and view it in the Viewer.
2 . Load Read1 into Framecycler by clicking Read1 and pressing Alt/option-F. (If you are using the PLE version of Nuke, simply click Play in the Viewer.)
3 . Zoom in close to the area in the image where the spoon is, place your mouse pointer over the edge of the spoon handle, and don’t move it (FigUrE 5.2).
Notice how much film weave there is in this plate. Film weave is the result of the celluloid moving a little inside the camera when shooting on film. You will fix that weave and add some flares to the candle flames.
FIGURE 5 .2 Placing the mouse pointer and not moving it is a good way to gauge movement.
4 . Quit Framecycler, or press Stop in the Viewer.
5 . Select Read1 and attach a Tracker node to it from the Transform toolbox.
6 . Make sure you’re viewing the output of Tracker1 in both the Viewer and frame 1.
The Tracker node’s Properties panel loads into the Properties Bin and looks like FigUrE 5.3. Using these controls and the on-screen controls, you can track a fea-ture in the image by defining the pattern box and using the Properties panel.
Tracking buttons Clear tracking
data
Trackers
7 . In the Viewer, click the center of the tracker point, where it says track1, and move it to the edge of the spoon handle (FigUrE 5.4).
FIGURE 5 .4 Placing the tracker point on a good tracking location.
8 . In Tracker1’s Properties panel click the forward play–looking button, which is the Track Forward button (FigUrE 5.5).
Track backward Track frame forward
Track forward
Track range forward
Track frame backward Track range backward
FIGURE 5 .5 Pressing the Track Forward button will start tracking to the end of the clip.
The Tracker node starts to follow the pixels inside the pattern box from frame to frame. A Progress Bar displays showing you how long before the Tracker (shorthand for Tracker node) finishes. When the Tracker finishes processing, FIGURE 5 .3 The
Tracker node’s Properties panel.
the tracking part of your work is actually finished. Anything beyond this is not really tracking—it’s applying a Tracker’s result. You can see the Tracker-accumulated tracking data in the track1.x and track1.y fields in the Properties panel as keyframes (FigUrE 5.6).
FIGURE 5 .6 The Tracker’s accumulated data is held in these fields as animation keyframes.
9 . Move back in the Timebar using the left arrow key.
Look at the track1.x and track1.y fields and how they change to reflect the position of the pattern box in each frame.
If you subtract the X and Y values in frame 1 from the X and Y values in frame 2, the result will be the movement you need to match the tracked movement. If you take that number and invert it (5 becomes –5), you will negate the movement and stabilize the shot. You can do that for any frame. The frame you are subtracting—
in this example, it is frame 1—is called the reference frame.
Now that you’ve successfully tracked the position of the spoon from frame to frame, you probably want to use this to stabilize the shot. This is done in another tab in the Tracker Properties panel.
10 . In Tracker1’s Properties panel, click the Transform tab.
11 . Choose Stabilize from the Transform drop-down menu (FigUrE 5.7).
FIGURE 5 .7 Using the tracking data to stabilize.
This is all you need to do to stabilize the shot. To make sure the shot is now stabi-lized, compare it in the Viewer to the unstabilized shot.
12 . Select Read1 in the DAG and press 2 on your keyboard.
13 . In the Viewer change the center control in the Viewer Composite Control drop-down menu from – to Wipe.
14 . Reposition the axis from the center of the frame to just above the spoon handle.
Notice that Tracker1’s transform controls are in the way. You need to get rid of this to see the Viewer properly.
15 . Close all Properties panels by clicking the Empty Properties Bin button at the top of the Properties Bin.
16 . Press Play in the Viewer and look at both sides of the wipe (FigUrE 5.8).
You can clearly see the stabilization working.
FIGURE 5 .8 Wiping between the stabilized and jittery versions of the sequence.
17 . Press Stop and change the center control in the Viewer Composite Control drop-down menu back to –.
18 .Click Tracker1 and press the 1 key to make sure you’re viewing that part of the branch.
Creating an image that is absolutely still is one reason to stabilize a shot. Another reason is to have an easier life when compositing. Instead of match-moving each element (as you do in the next exercise), you can stabilize the shot, comp it, and then bring back the motion using the tracked data you already accumulated. You do this to make compositing a lot easier and so your shot doesn’t stand out from the rest of the movie for being absolutely steady.
For this shot, the director asked to “bloom” each candle flame a little. You will add a flare to each candle flame using a node called, you guessed it, Flare from the Draw toolbox.
19 . Select Tracker1 and from the Draw toolbox add a Flare node (FigUrE 5.9).
20 . Drag the center of the flare on the center of the right-most candle flame using the on-screen controls, as shown in FigUrE 5.10.
I don’t have room to explain every property for the Flare node. It’s a very involved and very artistic—hence subjective—tool, which makes it difficult to teach. And let’s face it, it has a lot of properties. I encourage you to play with it and see its capabilities, but as far as it applies to tracking, you’ll copy some numbers from the list in the next step.
Note The Flare node is a great, very broad tool for creating various types of flares and lighting artifacts.
FIGURE 5 .9 A new node, Flare1, is inserted after Tracker1.
FIGURE 5 .10 Placing the center of the flare on the center of the flame.
21 . Copy the following values into the corresponding properties one by one and see what each does. When you’re done copying, if you want you can change them to suit your taste:
•
Radius = 0, 0, 50•
Ring Color = 1, 0.8, 0.3•
outer Falloff = 2.3, 2.65, 2.65•
Chroma Spread = 0.1•
Edge Flattening = 6•
Corners = 12The result of the Flare node should look a lot like FigUrE 5.11.
FIGURE 5 .11 The flare after treatment.
Now use this Flare to place three more flares in the shot.
22 . Copy Flare1 by clicking it and pressing Ctrl/Cmd-C.
23 . Make sure Flare1 is still selected and paste another flare by pressing Ctrl/Cmd-V.
You want to move the location of Flare2 to the second candle from the right. This can get confusing because when you paste a node, its Properties panel doesn’t automati-cally load into the Properties Bin, so moving the on-screen control now moves the position for Flare1. You have to be careful which on-screen control you’re using.
24 . Close Flare1’s Properties panel.
25 . Double-click Flare2 to load its Properties panel.
26 . Move Flare2’s position to the second candle.
27 . Repeat the process twice more for the other two candles.
Your image should have four flares on it—one on each candle. Your tree should look like FigUrE 5.12.
What’s left to do now is to bring back the film weave you removed in the first step.
You already have all the tracking data in Tracker1. You can now copy it and insert it at the end of the tree to bring back the transformation that you removed before.
28 . Copy Tracker1, click Flare4, and paste.
Tracker2 is then inserted after Flare4.
When you return a composited shot, it’s important to return it exactly as it was provided—except for making the changes requested. Your shot, remember, is often just one in a sequence.
29 . Double-click Tracker2 to open its Properties panel.
30 . Click the Transform tab and choose Match-move from the Transform drop-down menu.
31 . Make sure you’re viewing Tracker2 in the Viewer.
32 . Click Play in the Viewer.
You can see that the motion data was returned as it was before, except now it has flares, which are weaving just like the rest of the picture.
33 . Save your project in your student_files directory with a name you find fitting.
34 . Press Ctrl/Cmd-W to close the Nuke script and create a fresh one.
Next you will go deeper into tracking.
FIGURE 5 .12 Four Flare nodes inserted one after the other.
Note Keep in mind that every time you move an image around, some filtering occurs. Filtering means a kind of little blur that degrades the image a little. Moving an image twice like this creates two levels of filtering.
Doing that a lot will in effect soften your image.
on occasion this is a must, but in general you should avoid it. Here it served as a good way to show both stabilizing and match-moving together.